Previous studies in our laboratory have shown marked effects of hyperoxia in the atmosphere surrounding fetal mouse kidney and lung tissue in organ culture. Current studies explore the interrelationship of inorganic ions (Na, K, Ca, Mg) in modifying the destructive effects of oxygen. In addition, we are attempting to quantitate the concentrations of super oxide dismutase in fetal tissues. This enzyme is protective against the toxic effect of oxygen. Current research evaluates the beneficial effect of a variety of antioxidants (drugs) such as corticosteroids, chloroquin, alpha tocopherol, and retinoic acid in modifying the toxic effects of oxygen. The ultimate goal is to devise methods for prevention of oxygen toxicity in incompletely developed tissues, such as found in the premature human infant.